In percutaneous transluminal angioplasty, a dilation catheter is inserted into an artery to dilate the artery. For this purpose, the typical dilation catheter has an inflatable balloon adjacent its distal end and a balloon inflation lumen through which the balloon is inflated and deflated. Inflation is accomplished by forcing an appropriate inflation liquid through the lumen to the balloon, and deflation is accomplished by withdrawing the liquid from the balloon. Inflation of the balloon dilates the adjacent regions of the artery to provide lower restriction to blood flow through the artery.
In carrying out the dilation procedure, it is necessary to repeatedly inflate and deflate the balloon to repeatedly dilate the artery. During the time that the balloon is inflated, blood flow through the artery is blocked. For this reason, it is necessary that the inflation and deflation of the balloon be carried out as rapidly as possible. This is difficult to do because the balloon inflation lumen is long and of small diameter, and consequently, the balloon inflation lumen presents a substantial resistance to the flow of the inflation liquid to and from the balloon.
One other complicating factor is that air must be purged from the balloon before the dilation catheter is used for its intended purpose. This can be accomplished, for example, by inserting a vent tube through the balloon inflation lumen into the balloon. A purging liquid is then introduced through the balloon inflation lumen, and the air within the balloon is vented through the vent tube. One example of such an arrangement is shown in Simpson et al U.S. Pat. No. 4,323,071. One problem with this procedure is that the insertion of the vent tube must be carefully carried out not to damage the ballon and may be cumbersome if the vent tube is attempted to be taken out to obtain a larger inflation lumen.